GM 8L transmission

Automatic transmission family produced by General Motors

Motor vehicle

8L 45 · 8L 90
Overview
Manufacturer	General Motors
Production	2014–
Body and chassis
Class	8-speed longitudinal automatic transmission
Related	ZF 8HP
Chronology
Predecessor	6L 45 · 6L 50 · 6L 80 · 6L 90
Successor	10L 80 · 10L 90 · 10L 1000

The Hydramatic 8L 45 is an eight-speed automatic transmission built by General Motors debuting in the 2016 Cadillac CT6. It is designed for use in longitudinal engine applications attached to the front-located engine^[1] with a standard bell housing. It is a hydraulic (hydramatic) design sharing much with the 8L 90 transmission.^[2] Estimated weight savings over the heavier duty 8L 90 is 33 lb (15 kg). Gear ratios used enable a wide 7.0 ratio spread.

The 8L 90 is an eight-speed automatic transmission built by General Motors. It is designed for use in longitudinal engine applications either attached to the front-located engine^[1] with a standard bell housing or in the rear of the car adjacent to the differential (as in the Corvette). It is a hydraulic (hydramatic) design. GM also produces a similar design with the smaller 8L 45.

Both gearboxes are based on the layout of the ZF 8HP transmission from 2008, with the only difference being that gearsets 1 and 3 are swapped.^[3]

Specifications

Gear Ratios^[a]^[4]
Gear Model	R	1	2	3	4	5	6	7	8	Total Span	Avg. Step	Compo- nents

8L 45 · M5N · 2015	−3.928	4.615	3.038	2.065	1.658	1.259	1.000	0.849	0.658	7.011	1.321	4 Gearsets 2 Brakes 3 Clutches
8L 90 · M5U · 2014	−3.818	4.560	2.971	2.075	1.688	1.270	1.000	0.845	0.652	6.999	1.320
ZF 8HP All · 2008^[b]	−3.297	4.696	3.130	2.104	1.667	1.285	1.000	0.839	0.667	7.043	1.322

^ Differences in gear ratios have a measurable, direct impact on vehicle dynamics, performance, waste emissions as well as fuel mileage
^ for comparison purposes only

Features
	8L 45 M5N^[5]	8L 90 M5U · N8X^[6]

Input Capacity
Maximum engine power	308 bhp (230 kW)^[a]	420 bhp (313 kW)^[b]
Maximum gearbox torque	550 N⋅m (406 lb⋅ft)^[a]	900 N⋅m (664 lb⋅ft)^[b]
Maximum shift speed	7,500/min	6,000/min
Vehicle
Maximum Validated Weight Gross Vehicle Weight · GVW	—	—
Maximum Validated Weight Gross Curb Vehicle Weight · GCVW	12,000 lb (5,440 kg)^[a]	22,500 lb (10,210 kg)^[b]
Structure
Range-selector quadrant	P · R · N · D · M · L
Case description	2-piece main, bell integrated with main
Case material	Die cast aluminum
Shift pattern (2)	2 on/off solenoids
Shift quality	6 Variable Force Solenoids · 1 for each clutch · 1 for TCC
Torque converter clutch	Variable Force Solenoid ECCC · 2 path · turbine damper
Converter size	238 mm (9.37 in)	258 mm (10.16 in)
Fluid type	DEXRON High Performance ATF
Fluid capacity	10.8 L (11.4 US qt)^[a]	10.3 L (10.9 US qt)^[b]
Weight	80 kg (176 lb)^[a]	98.9 kg (218 lb)^[b]
Available Control Features
Shift Patterns	Multiple (Selectable)
Driver Shift Control	Tap Up and Down
Additional Modes	Tow & Haul Mode (Selectable)
Engine Torque Management	On All Shifts
Shift Control	Automatic Start/Stop Automatic Grade Braking
Assembly sites	GMPT^[c] Toledo · Ohio · USA GMPT^[c] Silao · Mexico

^ ^a ^b ^c ^d ^e based on 2020 Chevrolet Colorado Z71 2WD Crew Cab · Short Bed ^ ^a ^b ^c ^d ^e General Motors estimate ^ ^a ^b General Motors Powertrain

In-Depth Gear Ratios
With Assessment			Planetary Gearset: Teeth^[a]				Count	Total	Avg.

Model Type	Max. Input Torque First Delivery		S₁^[b] R₁^[c]	S₂^[d] R₂^[e]	S₃^[f] R₃^[g]	S₄^[h] R₄^[i]	Brakes Clutches	Ratio Span	Gear Step^[j]
Gear Ratio	R ${i_{R}}$	1 ${i_{1}}$	2 ${i_{2}}$	3 ${i_{3}}$	4 ${i_{4}}$	5 ${i_{5}}$	6 ${i_{6}}$	7 ${i_{7}}$	8 ${i_{8}}$
Step	$-{\tfrac {i_{R}}{i_{1}}}$ ^[k]	${\tfrac {i_{1}}{i_{1}}}$	${\tfrac {i_{1}}{i_{2}}}$ ^[l]	${\tfrac {i_{2}}{i_{3}}}$	${\tfrac {i_{3}}{i_{4}}}$	${\tfrac {i_{4}}{i_{5}}}$	${\tfrac {i_{5}}{i_{6}}}$	${\tfrac {i_{6}}{i_{7}}}$	${\tfrac {i_{7}}{i_{8}}}$
Step 2^[m]			${\tfrac {i_{1}}{i_{2}}}:{\tfrac {i_{2}}{i_{3}}}$	${\tfrac {i_{2}}{i_{3}}}:{\tfrac {i_{3}}{i_{4}}}$	${\tfrac {i_{3}}{i_{4}}}:{\tfrac {i_{4}}{i_{5}}}$	${\tfrac {i_{4}}{i_{5}}}:{\tfrac {i_{5}}{i_{6}}}$	${\tfrac {i_{5}}{i_{6}}}:{\tfrac {i_{6}}{i_{7}}}$	${\tfrac {i_{6}}{i_{7}}}:{\tfrac {i_{7}}{i_{8}}}$
Shaft Speed	${\tfrac {i_{1}}{i_{R}}}$	${\tfrac {i_{1}}{i_{1}}}$	${\tfrac {i_{1}}{i_{2}}}$	${\tfrac {i_{1}}{i_{3}}}$	${\tfrac {i_{1}}{i_{4}}}$	${\tfrac {i_{1}}{i_{5}}}$	${\tfrac {i_{1}}{i_{6}}}$	${\tfrac {i_{1}}{i_{7}}}$	${\tfrac {i_{1}}{i_{8}}}$
Δ Shaft Speed	$0-{\tfrac {i_{1}}{i_{R}}}$	${\tfrac {i_{1}}{i_{1}}}-0$	${\tfrac {i_{1}}{i_{2}}}-{\tfrac {i_{1}}{i_{1}}}$	${\tfrac {i_{1}}{i_{3}}}-{\tfrac {i_{1}}{i_{2}}}$	${\tfrac {i_{1}}{i_{4}}}-{\tfrac {i_{1}}{i_{3}}}$	${\tfrac {i_{1}}{i_{5}}}-{\tfrac {i_{1}}{i_{4}}}$	${\tfrac {i_{1}}{i_{6}}}-{\tfrac {i_{1}}{i_{5}}}$	${\tfrac {i_{1}}{i_{7}}}-{\tfrac {i_{1}}{i_{6}}}$	${\tfrac {i_{1}}{i_{8}}}-{\tfrac {i_{1}}{i_{7}}}$

8L 45 M5N	550 N⋅m (406 lb⋅ft) 2015^[n]		41 79	41 79	41 79	26 94	2 3	7.0107	1.3208^[j]
Gear Ratio	−3.9278^[k] $-{\tfrac {4,187}{1,066}}$	4.6154 ${\tfrac {60}{13}}$	3.0385^[o] ${\tfrac {79}{26}}$	2.0648 ${\tfrac {7,200}{3,487}}$	1.6583^[j]^[o]^[p] ${\tfrac {199}{120}}$	1.2587^[o] ${\tfrac {740,760}{588,527}}$	1.0000 ${\tfrac {1}{1}}$	0.8494^[o]^[p] ${\tfrac {9,480}{11,161}}$	0.6583 ${\tfrac {79}{120}}$
Step	0.8510^[k]	1.0000	1.5190	1.4715	1.2451^[j]	1.3175	1.2587	1.1773	1.2902
Step 2^[m]			1.0322^[o]	1.1819	0.9450^[o]	1.0468^[o]	1.0691	0.9125^[o]
Speed	–1.1751	1.0000	1.5190	2.2353	2.7831	3.6669	4.6154	5.4338	7.0107
Δ Speed	1.1751	1.0000	0.5190	0.7163	0.5479^[p]	0.8837	0.9485	0.8184^[p]	1.5769

8L 90 M5U	900 N⋅m (664 lb⋅ft)^[7] 2014^[q]		41^[8] 79	46 86	37 73	25 89	2 3	6.9991	1.3204^[j]
Gear Ratio	−3.8176^[k] $-{\tfrac {43,043}{11,275}}$	4.5600 ${\tfrac {114}{25}}$	2.9709^[o] ${\tfrac {817}{275}}$	2.0751 ${\tfrac {12,540}{6,043}}$	1.6876^[j]^[o]^[p] ${\tfrac {4,121}{2,442}}$	1.2700^[o] ${\tfrac {28,817,100}{22,690,429}}$	1.0000 ${\tfrac {1}{1}}$	0.8455^[o]^[p] ${\tfrac {5,160}{6,103}}$	0.6515 ${\tfrac {43}{66}}$
Step	0.8372^[k]	1.0000	1.5349	1.4317	1.2297^[j]	1.3288	1.2700	1.1828	1.2977
Step 2^[m]			1.0721^[o]	1.1643	0.9254^[o]	1.0463^[o]	1.0738	0.9114^[o]
Speed	–1.1945	1.0000	1.5349	2.1975	2.7021	3.5905	4.56	5.3933	6.9991
Δ Speed	1.1945	1.0000	0.5349	0.6626	0.5047^[p]	0.8884	0.9695	0.8333^[p]	1.6057

Ratio^[r] R & even	$i_{R}={\tfrac {R_{2}(S_{1}S_{4}-R_{1}R_{4})}{S_{1}S_{4}(S_{2}+R_{2})}}$		$i_{2}={\tfrac {R_{2}(S_{4}+R_{4})}{(S_{2}+R_{2})S_{4}}}$		$i_{4}=1+{\tfrac {S_{2}R_{3}}{S_{3}(S_{2}+R_{2})}}$		$i_{6}={\tfrac {1}{1}}$	$i_{8}={\tfrac {R_{2}}{S_{2}+R_{2}}}$
Ratio^[r] odd	$i_{1}={\tfrac {S_{4}+R_{4}}{S_{4}}}$		${\tfrac {(S_{3}+R_{3})(S_{4}+R_{4})}{S_{4}R_{3}+S_{3}(S_{4}+R_{4})}}$		${\tfrac {S_{3}R_{2}R_{4}(S_{1}+R_{1})+S_{2}S_{1}(S_{3}+R_{3})(S_{4}+R_{4})}{S_{3}R_{4}(S_{1}(S_{2}+R_{2})+R_{1}R_{2})+S_{1}S_{2}S_{4}(S_{3}+R_{3})}}$			${\tfrac {R_{2}(S_{1}+R_{1})}{R_{2}(S_{1}+R_{1})+S_{1}S_{2}}}$
Algebra And Actuated Shift Elements^[s]
Brake A^[t]	❶	❶	❶					❶	❶
Brake B^[u]	❶	❶	❶	❶	❶	❶
Clutch C^[v]		❶		❶		❶	❶	❶
Clutch D^[w]	❶				❶	❶	❶	❶	❶
Clutch E^[x]			❶	❶	❶		❶		❶

8HP 70 ^[y]^[z]	700 N⋅m (516 lb⋅ft) 2008		48^[9] 96	48^[9] 96	69^[10] 111	23^[10] 85	2 3	7.0435	1.3216^[j]
Gear Ratio	−3.2968^[k] $-{\tfrac {1,744}{529}}$	4.6957 ${\tfrac {108}{23}}$	3.1304^[o] ${\tfrac {72}{23}}$	2.1039 ${\tfrac {162}{77}}$	1.6667^[j]^[o]^[p] ${\tfrac {5}{3}}$	1.2845^[o] ${\tfrac {8,826}{6,871}}$	1.0000 ${\tfrac {1}{1}}$	0.8392^[o]^[p] ${\tfrac {120}{143}}$	0.6667 ${\tfrac {2}{3}}$
Step	0.7021^[k]	1.0000	1.5000	1.4879	1.2623^[j]	1.2975	1.2845	1.1917	1.2587
Step 2^[m]			1.0081^[o]	1.1787	0.9729^[o]	1.0101^[o]	1.0779	0.9467^[o]
Speed	–1.4243	1.0000	1.5000	2.2319	2.8174	3.6555	4.6957	5.5965	7.0435
Δ Speed	1.4243	1.0000	0.5000	0.7319	0.5855^[p]	0.8382	1.0401	0.9000^[p]	1.4478

Ratio^[aa] R & even	$i_{R}={\tfrac {R_{2}(S_{3}S_{4}-R_{3}R_{4})}{S_{3}S_{4}(S_{2}+R_{2})}}$		$i_{2}={\tfrac {R_{2}(S_{4}+R_{4})}{(S_{2}+R_{2})S_{4}}}$		$i_{4}=1+{\tfrac {S_{2}R_{1}}{S_{1}(S_{2}+R_{2})}}$		$i_{6}={\tfrac {1}{1}}$	$i_{8}={\tfrac {R_{2}}{S_{2}+R_{2}}}$
Ratio^[aa] odd	$i_{1}={\tfrac {S_{4}+R_{4}}{S_{4}}}$		${\tfrac {(S_{1}+R_{1})(S_{4}+R_{4})}{S_{4}R_{1}+S_{1}(S_{4}+R_{4})}}$		${\tfrac {S_{1}R_{2}R_{4}(S_{3}+R_{3})+S_{2}S_{3}(S_{1}+R_{1})(S_{4}+R_{4})}{S_{1}R_{4}(S_{3}(S_{2}+R_{2})+R_{2}R_{3})+S_{2}S_{3}S_{4}(S_{1}+R_{1})}}$			${\tfrac {R_{2}(S_{3}+R_{3})}{R_{2}(S_{3}+R_{3})+S_{2}S_{3}}}$

^ Layout • Input and output are on opposite sides • Planetary gearset 1 is on the input (turbine) side • Input shafts are C₂ and, if actuated, R₁ and S₄ • Output shaft is C₄ (planetary gear carrier of gearset 4) ^ Sun 1: sun gear of gearset 1 ^ Ring 1: ring gear of gearset 1 ^ Sun 2: sun gear of gearset 2 ^ Ring 2: ring gear of gearset 2 ^ Sun 3: sun gear of gearset 3 ^ Ring 3: ring gear of gearset 3 ^ Sun 4: sun gear of gearset 4 ^ Ring 4: ring gear of gearset 4 ^ ^a ^b ^c ^d ^e ^f ^g ^h ⁱ ^j Standard 50/50: 50/50 are above/below average step With consistently falling gear steps (row highlighted in yellow), the lower half of them (rounded down, here the first three) is always larger and the upper half of them (rounded up, here the last four) is always smaller than the average gear step (cell highlighted in yellow two rows above). Deviating gear steps (red bold) indicate an unfavorable gearset selection ^ ^a ^b ^c ^d ^e ^f ^g Standard REV: reverse gear is similar to 1^st gear Reverse and 1^st gear should have the same ratio. Plus 11 % minus 10 % compared to 1^st gear is good, plus 25 % minus 20 % is acceptable (red); even larger deviations (bold) can impair the driving experience, especially when towing a trailer. A torque converter can only partially compensate for this deficiency ^ Standard FIRST: gear step 1^st to 2^nd gear With consistently falling gear steps, the largest gear step is the one from the 1^st to the 2^nd gear, although it should be limited for a smooth gear shift. A ratio step of up to 5 : 3 (1.6667 : 1) is good, up to 7 : 4 (1.7500 : 1) is acceptable (red); above (bold) is unsatisfactory ^ ^a ^b ^c ^d From right to left ^ Model year 2016 ^ ^a ^b ^c ^d ^e ^f ^g ^h ⁱ ^j ^k ^l ^m ⁿ ^o ^p ^q ^r ^s ^t ^u ^v ^w ^x Standard SECOND: 2^nd degree steps above 1 With consistently rising (from right to left) gear steps, each 2^nd degree step (first row highlighted in green) is larger than 1. Smaller than its predecessor is acceptable (red); smaller than 1 (bold) is unsatisfactory ^ ^a ^b ^c ^d ^e ^f ^g ^h ⁱ ^j ^k ^l Standard SPEED: shaft speed difference increase One difference that runs counter to the consistent increase in shaft speed differences (second row highlighted in green) is acceptable (red); two consecutive ones (bold) indicate an unfavorable gearset selection ^ Model year 2015 ^ ^a ^b Adjusted formulas with gearset 1 and 3 swapped ^ S₁ and R₂ share a common shaft C₁ and C₄ share a common shaft S₂ and S₃ share a common shaft C₃ (carrier 3) and R₄ share a common shaft ^ Blocks S₂ and S₃ ^ Blocks R₃ ^ Couples C₂ and S₄ with the turbine ^ Couples R₁ with S₄ ^ Couples S₁ and R₂ with S₄ ^ without generation designation ^ First transmission on the market to use the dedicated 8-speed layout gearset 1 and 3 not swapped ^ ^a ^b Original formulas with gearset 1 and 3 not swapped

Applications

8L 45
Make	Model Years	Model
Cadillac	2016–2019	ATS
	2016–2019	CTS
	2020–present	CT4
	2016–present	CT6
Chevrolet	2016–2019	Camaro
Chevrolet	2017–present	Colorado
GMC	2017–present	Canyon

8L 90
Make	Model Years	Model	Final Drive Ratio
Cadillac	2015–2017	Escalade^[11]	3.23
	2016–present	ATS-V	2.85
	2016–present	CTS-V	2.85
	2016–present	CT6	3.27
Chevrolet	2015–2019	Corvette (C7) Stingray^[12]	2.41^[a] or 2.73^[b]
	2015–2019	Corvette (C7) Z06^[13]	2.41
	2019	Corvette (C7) ZR1	2.73
	2015–present	Silverado^[14]	3.23^[a] or 3.42^[c]
	2015–present	Colorado	3.42
	2016–2018	Camaro SS	2.77
	2017–present	Express^[d]
GMC	2015–2017	Yukon Denali · Denali XL	3.23
	2015–present	Sierra^[14]	3.23
	2015–present	Canyon	3.42
	2017–present	Savana^[d]

^ ^a ^b Standard ^ Z51 ^ Maximum Trailering Package ^ ^a ^b 2.8 L diesel engine and 4.3 L gas engine only

Lawsuits

The 8L 90 is the subject of a class-action lawsuit filed in December 2018 that alleges the transmission suffers from persistent "shudder" issues and that GM has known about the problems since its introduction and has failed to provide a solution, instead choosing to wait until the unit is out of warranty.^[15]

References

^ ^a ^b "USA Information Guide Model Year 2018" (PDF). Retrieved 15 July 2019.
^ "Cadillac Introduces New 8-Speed Automatic on CT6". Cadillac Media USA. Cadillac Media USA. 20 March 2015. Retrieved 20 March 2015.
^ "Timur Apakidze · Saturation Dive: The GM 8L 90 8-Speed Transmission". TTAC: The Truth About Cars. 23 April 2014. Retrieved 12 April 2024.
^ "New 8-Speed Enables Quicker, More Efficient Corvette". www.gm.com. General Motors. 20 August 2014. Archived from the original on 22 December 2014. Retrieved 21 August 2014.
^ https://poweredsolutions.gm.com/products/8l45-8-speed-transmission/
^ https://poweredsolutions.gm.com/products/8l90-8-speed-transmission/
^ "Transmission Repair Cost Guide". Retrieved 15 July 2019.
^ "WIT · Whatever It Takes · Automatic Transmission Parts Catalog 2018+2019 Page 268". Retrieved 15 July 2019.
^ ^a ^b 8HP 70 Repair Manual · Picture 10106 p. 110 · Saarbruecken 2014 · https://avtgr.ru/upload/data/pdf/zf_instructions/8HP70.pdf
^ ^a ^b "Timur Apakidze · Saturation Dive: ZF 8-Speed Automatic". TTAC: The Truth About Cars. 11 March 2014. Retrieved 7 July 2019.
^ "2015 Cadillac Escalade Updated with 8L90 8-Speed Automatic and More Tech [Photo Gallery]". 11 August 2014. Retrieved 12 August 2014.
^ "Chevrolet Confirms 2015 Corvette Stingray To Utilize 8L90 Eight-Speed Gearbox". Retrieved 9 April 2014.
^ "Supercharged 2015 Chevy Corvette Z06 takes the C7 beyond the ZR1 [w/video]". Retrieved 25 January 2014.
^ ^a ^b "GM confirms 2015 Silverado, Sierra to get 8-speed automatic". Retrieved 18 June 2014.
^ "Class Action Lawsuit Filed Over Alleged Shifting Defect in Certain General Motors Transmissions". 19 December 2018. Retrieved 2 February 2019.